US3776991A - Injection blow molding method - Google Patents

Abstract

An injection blow molding method utilizing a rotary indexing plate on which core rod assemblies are mounted for indexing, in a rotary path, through at least three stations. The first station is an injection station at which a plastic parisian or preform is injected around the core rod and within a neck mold. The second station is a blow station at which air passes through the core rod into the parisian thereby inflating it and forcing it against the surface of the selected blow mold cavity. The third station is an ejection station at which the finished plastic container is removed from the core rod and neck mold. In some applications there are four stations. The fourth stations could be used to preheat or precool the core rods preparing them for the start of the ejection cycle. The fourth station in a suggested embodiment could be deployed for preparing for orientation the plastic parisian by temperature control; and, thereafter, orientation takes place prior to blowing. obviously the tree and four station machine can be modulated to present a six and eight station machine respectively. In one embodiment, the core rods and supporting indexing plate are vertically reciprocal into and out of the injection mold, blow mold and removal mechanism. In another embodiment, the core rod assemblies do not reciprocate but the associated injection and blow molds and finished product removal mechanism are mounted for vertical reciprocation on a clamp plate. The blown finished containers are indexed to the ejection station at which the containers are removed from the machine. In the event the neck mold is one-piece construction and the container neck includes threads, an unscrewing device acts to remove the bottle from the mold. If a neck mold of multiple section construction is utilized, the neck mold is opened by suitable mechanical means.

Description

Dec. 4, 1973 MARCUS 3,776,991

INJECTION BLOW MOLDING METHOD Filed June 50, 1971 9 Sheets-Sheet 1.

ATTOR N EYS Dec. 4, 1973 P. MARCUS 3,776,991

I INJECTION BLOW MOLDING METHOD Filed June 30, 1971 9 Sheets-Sheet 3 a H m U Lk VENTOR M ecu;

ATTO R N EYS Dec. 4, 1973 P. MARCUS 3,776,991

INJECTION BLOW MOLDING METHOD v Filed June 30, 1971 9 Sheets-Sheet -1 INVENTOR PAUL NAR VS ATTORNEYS P. MARCUS Dec. 4, 1973 INJECTION BLOW MOLDING METHOD Filed June 30,

9 Sheets-Sheet 5 IIIIIIIIHH lllillllllllm B111! l I l HIHW lll

INVENTOR.

Dec. 4, 1973 P. MARCUS 3,776,991

INJECTION BLOW MOLDING METHOD Filed June 30, 1971 9 Sheets-Sheet e 7 /Z44 Z R/Z \\ve -mi x zfiz L INVENTOR L 1 I 1 P404 NflRCVS ATTORNEYS P. MARCUS INJECTION BLOW MOLDING METHOD Dec 4, 1973 9 Sheets-Sheet 7 Filed June 30, 1971 F/Gn/Jd INVENTOR PAZ A NflAC'US ATTORNEYS Dec. 4, 1973 P. MARCUS 3,776,991

INJECTION BLOW MOLDING METHOD Filed June 30, 1971 9 Sheets-Sheet 9 4 5 3 R a, a M m 5 dM/f d \L U 3 m m 0 /m E C 4 m u 2 H E 8 H m 44 n 4 M H n .l w H 1 I 4 I 1 Z 1 v I 1 4 M H H i m you, llll l I 4 M Q? a Z w .1 4 m El I HHUHJJ ..fl| l M 4 HUG h I H. I IHHIWILL J fil Q m 4 I w i I I 1 a H n 2 M m d J F L 8 Claims ABSTRACT OF THE DISCLOSURE An injection blow molding method utilizing a rotary indexing plate on which core rod assemblies are mounted for indexing, in a rotary path, through at least three stations. The first station is an injection station at which a plastic parison or preform is injected around the core rod and within a neck mold. The second station is a blow station at which air passes through the core rod into the parison thereby inflating it and forcing it against the surface of the selected blow mold cavity. The third station is an ejection station at which the finished plastic container is removed from the core rod and neck mold. In some applications there are four stations. The fourth station could be used to preheat or precool the core rods preparing them for the start of the ejection cycle. The fourth station in a suggested embodiment could be deployed for preparing for orientation the plastic parison by temperature control; and, thereafter, orientation takes place prior to blowing. Obviously the three and four station machine can be modulated to present a six and eight station machine respectively. In one embodiment, the core rods and supporting indexing plate are verticall reciprocal into and out of the injection mold, blow mold and removal mechanism. In another embodiment, the core rod assemblies do not reciprocate but the associated injection and blow molds and finished product removal mechanism are mounted for vertical reciprocation on a clamp plate. The blown finished containers are indexed to the ejection station at which the containers are removed from the machine. In the event the neck mold is of one-piece construction and the container neck includes threads, an unscrewing device acts to remove the bottle from the mold. If a neck mold of multiple section construction is utilized, the neck mold is opened by suit-able mechanical means.

The present invention relates to a method for making hollow plastic articles such as containers or bottles, by first injection molding a preform or parison and then transferring it to a position at which it is blown into conformation with the finished mold. An object of this invention is to provide an improved blow molding method in which a plurality of parisons are injection molded and thereafter transferred to a blow molding station at which the parisons are blown into finished shape, following which the formed articles are transferred to an ejection station for removal from the apparatus.

Another object is to provide an improved injection blow molding method which minimizes if not eliminates the parting line on a container neck finish and/or a parison.

United States Patent A further object is to upgrade injection blow molding production while minimizing cycle time by utilizing a multiple station molding technique including injection, blowing and ejection stations which are separate but adapted to be operated simultaneously.

Still another object is to provide a multiple station injection blow molding method of the foregoing type in 3,776,991 Patented Dec. 4, 1973 preforms in a method of the foregoing type for optimum speed, product control and output.

An important object is to provide a method of the foregoing type in which a station may be intoduced for preparing and mechanically orienting the plastic parison to permit the resin to obtain its optimum properties prior to blowing.

Another important object is to utilize a parison preparation station prior to blowing in order to obtain increased blow-up ratios heretofore unrealized.

Other objects and advantages will be enumerated and also apparent from the following detailed description which is to be taken in conjunction with the accompanying drawings in which:

FIG. 1 is a top plan view of an indexing three station injection blow molding apparatus of this invention;

FIG. 2. is a side elevational view thereof showing a formed finished container in phantom at the ejection station;

FIG. 3 is a longitudinal sectional view of an indexing core assembly with a neck mold associated therewith and an open preform or parison forming mold of the injection station;

FIG. 4 is similar to FIG. 3 showing the parison mold in a closed position about the core rod to enable the injection molding of the parison;

FIG. 5 is a longitudinal sectional view of the core assembly and formed parison shown indexed to the blowing station with the blow mold in an open position;

FIG. -6 is similar to FIG. 5 showing the blow mold closed about the core assembly with the parison blown into conformation with the blow mold die cavity walls;

FIG. 7 shows the blown article about the core rod and the blow mold in its open position;

FIG. 8a is a longitudinal sectional view showing the core assembly and associated blown article indexed to the ejection station at which an unscrewing mechanism operates to remove the blown article from the core rod;

FIG. 8b is similar to FIG. 8a but showing another form or article unscrewing mechanism;

FIG. 9 is top plan view of a six station injection blow molding machine in accordance with the present invention;

FIG. 10 is a side elevational view thereof showing a formed article in an upright position at the ejection station;

FIG. 11 is a top plan view of a four station injection blow molding machine of this invention in which a plastic orientation preparation station is interposed between the parison injection and blow molding stations;

FIG. 12 is a longitudinal sectional view of the core assembly and associated parison at the orientation preparation station at which the parison is expanded slightly away from the surfaces of the core pin and brought to correct orientation temperature;

FIG. 13a is a longitudinal sectional view of the slightly expanded parison and core assembly at the blow molding station at which the blow mold is closed about the parison prior to orientation by mechanical stretching prior to blowing;

FIG. 13b is a similar view showing the parison stretched mechanically prior to blowing;

FIG. 14 is a similar view showing the stretched parison blown into conformation with the walls of the blow mold cavity;

FIG. 15 is a longitudinal sectional view at the ejection station showing the opening of a split neck mold by diverging cam pins prior to product removal;

FIG. 16 is a top plan view of an injection blow molding machine having more than one row of core rod assemblies at each station; and

FIG. 17 is a side elevational view thereof.

tions are provided, namely apreform or parison injection station 20, blowing station 22 and an ejection station 24. Core rod assemblies 26a, 26b and 26c extend upwardly towards the respective stations and are mounted on a rotary indexing plate 28 for movement to and from each station. The rotary indexing plate is supported for rotation by bed plate 30 which has associated therewith an indexing mechanism 32 for indexing the plate 28 in a manner well known to the molding art. As will be explained, the index mechanism can be vertically raised and lowered to provide for several mechanical actions.

The core rod assemblies 26 are adapted to be associated with each of the stations by rendering the latter vertically reciprocal towards and away the former. In this connection the stations 20, 22 and 24 extend downwardly from the vertically reciprocating clamping plate 34 which is supported by a number of jacking or clamping cylinder assemblies 36 extending downwardly from a stationary frame 38 of the machine. A jacking cylinder 37 is preferably provided at the parison injection molding station.

At the injection station 20, shown in detail in FIGS. 3 and 4, is a plastic preform or parison 40. Although a single core rod assembly is shown at each station, it should be understood that rows or arrays of multiple core rod assemblies may be employed with the associated molds and product removal mechanisms for purposes of increasing molding and production of the selected articles. Thus, the illustrated single core rod assembly 26a at the parison station is mounted on an assembly plate 42 from which extends vertical core rod 44. This rod 44 includes an axial passage 46 which is adapted to communicate with passage 48 in plate 42 coupled in turn with a source of air. A poppet valve 50 maintains the upper end of passage 46 closed because of the bias of spring 52 which acts upon disc 54 which is at the bottom end of the valve stem 56. In the illustrated embodiment the core rod assembly 2611 also includes a one piece-neck mold 58 having a die cavity 60 of a threaded nature for forming threads on the neck of a container, bottle or jar as the case may be.

The parison injection mold 62 at injection station 20 is mounted by manifold or plate 64 extending downwardly from clamp plate 34. In all cases the hot plastic resin is injected through a single or multi-nozzle metering device into the parison mold 62 as well as neck mold 58. In the case of multiple nozzle metering and manifolding reference is made to US. Pat. No. 3,535,742. Suflice it to say that upon downward reciprocation of the clamp plate 34 the parison mold 62 will be lowered about the core pin 44 into engagement with the neck mold 58 to define the parison forming cavity 66. The parison 40 is formed wherein the selected plasticator or extruder (not shown) injects the selected plastic melt under controlled prressure into the selected single or multiple nozzle manifold 68. This device which may assume the form of the device disclosed in the above referenced patent acts as a reservoir in holding the plastic melt at a controlled temperature. The melt is distributed to the individual injection nozzles or gates as the case may be'which, in turn, cause the plastic to fill eachof the parison cavities 66. As discussed in the patent, should a multi-nozzle manifold be incorporated, the plastic is injected in such a manner that all cavities 66 fill simultaneously (or not simultaneously according to requirements), whereby all cavities will have the contained parison at uniform density, pressure and temperature. As will be appreciated where more than one core assembly is provided at each station, the cavities may not be the same size and, therefore, such uniformity will not be prescribed.

The cavity 66 is'carefully temperature controlled electrically or by fluids (water or oil in a manner well known to the art. These fluids may be cooled or chilled such that the cavity will have different heat zones permitting the maintenance of areas of the parison 40 at different temperatures to'nsure the desire'd'wall thickness, -orientation,

properties, and distribution of the finished plastic product.

7 Towards this end the core 44, parison mold 62 and neck mold 58 may be independently cooled or heated to form a skin on the parison outer and inner surfaces.

After the plastic parison 40 has been correctly seasoned in the parison mold 62, it is now ready for blowing. The clamp plate 34 will be reciprocated upwardly to elevate the air mold 62. The rotary indexing plate 28 and consequently the core assemblies 26 index to the next station. In the case of core assembly 26a, it will now rotate to station 22 previously occupied by core assembly 26b.

The blowing cycle starts by initially lowering the clamp plate 34 and index mechanism, which movement opens blow valves. The blow mold 70 at blowing station 22 may be of two or more parts as shown in FIGS. 5 and 6 which would include an upper vertically reciprocal or stationary die member 72 and laterally shiftable die members 74 and 76, each of which are mounted for reciprocal movement to the cylinder assemblies 78 and 80 respectively. The die member 72, 74 and 76 may be individually cooled or heated. When the clamp plate 34 is lowered, the blow mold 70 may be opened or in a clamped or closed position. In the case of the latter position, the closed blow mold 70, 74, 76 will be disposed about the core rod 44 while being clamped in closed position against the neck mold 58. In the event the blow mold 70 was in an open position, it will be clamp closed when the clamp plate 34 is completely lowered. When this occurs, the indexing plate 28 is lowered into coupling relation with the bed plate 30. Air enters from the bed plate 30 through seals to the index plate 28. The air seals are mounted on a spring device (not shown) which is held to the bed plate 30. This arrangement permits the bed plate 30 to float and thereby remain in relatively tight association with the index plate 28. The blown air then goes from the index plate 28 through an air pipe 82 into passage 48 of plate 42. If more than one core rod-assemblies and corre sponding blow molds are provided, the blown air is manifolded to each of the core rods 44. The poppet type blow valves 50 now open, which incidentally can be mechanically actuated as well where desired or for that matter be opened in any manner well known to the art. In any event blown air enters the parison 40 from the tip end of the core rod 44 or side, if desired. If other types and shapes of valves 50 are chosen depending on the design of the finished container, air may be made to enter at some other location, as for example through the core side walls near the neck mold 58. In any event the parison 40 is blown into conformation with the blow mold 70 to form the finished container 84. Thereafter, the blow mold 70 is opened and the clamping plate 34 is raised to permit the indexing plate 28 and consequently the core rod assembly 26a to be indexed to the ejection station 24.

When the core rod assembly 26a with blown container 84 comes to rest at the ejection station 24, the container may be removed in several ways. In the discussed embodiment and when employing a one-piece neck finish mold 58, the neck mold 58 may be stripped from the core rod 44 when the indexing plate is lowered from its normal position to its lowermost position in coupling relationship with the bed plate 30 (see FIG. 8a). Of course, this follows the lowering of the clamp plate 34 and when this occurs and the neck mold 58 as well as the finished container 84 is elevated relative to the core rod 44. This index mechanism eject stroke provides motion for mechanical action to strip or ejectparisons, finished products, open neck molds, open air valves, orient and blow the plastic parts. An unscrewing mechanism 86 unscrews and removes the container,84 from the neck mold 58. Further assistance can be given by air blown through the core rod 44. The exemplary unscrewing mechanism 86 may be in the form of one or more rotating wheels 88 or a rotatable continuous belt (not shown).

An alternating unscrewing mechanism 86' may be in the form of a rotatable rod 88' which engages with accommodating surfaces in the base of the container 84 which, where desirable or necessary, may include a keying or other arrangement afforded by the associated surfaces of the container 84 and rod 88'.

After the container 84 has been unscrewed from the neck mold 58, it is removed by any one of many known mechanisms in the art and thereafter transferred in the desired aligned or upright position. Where desired, these containers may be stacked and eventually packaged in suitable receptacles or containers.

The cycle of obtaining the finished product 84 as a result of the excursion and indexing of core assembly 26a through stations 20, 22 and 24 is repeated as is the case with the other core assemblies 26b and 26C.

In the embodiment of the invention illustrated in FIGS. 9 and 10, multiple core assemblies 126 are arranged in an array or other suitable arrangemnet on indexing plate 128. In this embodiment the indexing plate is disposed above the injection station 120, blowing station 122 and ejection station 124 which extend upwardly from a stationary bed plate 130. As Will be observed the machine of this embodiment includes six stations which include another set of injection station 120a, blowing station 122a and ejection station 124a. In this manner, the production of the machine is increased many fold. In all other respects the details of the machine of this embodiment correspond with that disclosed in the embodiment of FIGS. 1 to 8 and will bear similar numbers increased by 100.

-Referring now .to the embodiment of the invention shown in FIGS. 11 to 14, a fourth station 290 is mounted by means of the clamp plate 234 between the injection station 220 and blow station 222. The stations of this embodiment are located approximately 90 from one another and the indexing of the core assemblies 226 rotate this amount while indexing as compared to the 120 station separation and core assembly indexing of the embodiment of FIGS. 1 to 8'. In all other respects, the embodiment of FIGS. 11 to 14 are the same as the embodiment of FIGS. 1 to 8 and, accordingly, similar numbers will be employed increased by 200.

At the station 290 the injection parison is air separated from the associated core rod 244 into conformity with the walls of the interim closed or clamped mold halves 291 and 292 to temperature prepare the parison for further blow or orientation. These molds halves 291 and 292 are adapted to be opened hydraulically by the cylinder assemblies 293 and 294 respectively to permit indexing of the core assemblies 226. The cavity provided by the mold halves 291 and 292 is smaller than that defined by the blow mold 270 which defines the finished product 284. The principal purpose of the interim station 290 is to bring and maintain the parison to the optimum temperature for orientation. For this purpose experience has shown that minimal separation of the parison from the core pin 244 should be sought. Where it is desired to increase blow-up ratio, maximum separation is sought. In addition, the air pressure employed for purposes of separating the parison 240 from the core pin 244 should be maintained at a minimum. When the air separated parison of FIG. 12 is indexed to the next station 222 for blowing following opening of the mold halves 291 and 292, it will be disposed between the closed and clamped blow mold 270 (see FIG. 13b)v and there stretched mechanically. This is accomplished by mechanically shifting the poppet valve stem'295 in a manner suggested earlier herein; and that is illustrated in FIG. 13b incident to the closing of the space between indexing plate 228 and bed plate 230. The parison will thus be stretched or oriented mechanically prior to blowing as shown in FIG. 13b. When the index plate 228 and bed plate 230 are coupled the blowing cycle starts and the mechanically expanded parison is blown into conformity with the blow mold270 .as shown in FIG. 14. Obviously other mechanisms for stretching the parison prior to blowing may be employed as for example by the utilization of external means which grip the exterior of the parison of FIG. 12 and pull it upwardly to the desired extent.

In FIG. 15 a mechanism is illustrated for incorporation and mounting at the ejection station 24 as an alternative to the mechanisms illustrated in FIGS. 8a and 8b, especially when using a split neck mold 358. As will be appreciated, the finished container 384 is not unscrewed but rather simply released and then removed from the core rod 344 in any one of several manners such as by means of suction or vacuum in closely associated vacuum tube 396 which conveys the container 384 to the desired location. The split neck mold 358 may be parted or separated by any one of a number of techniques such as cams, toggles, hydrocyliuders, etc. and including the illustrated angle cam pins 397a and 397b which extend upwardly from plate 342 into accommodating holes 398a and 398b, respectively. Thus, as the neck mold 358 is pushed upwardly, as the index plate 328 and bed plate 330 are shifted into coupling relationship, the cam pins 397 separate the split mold 358. When the neck mold 358 is lowered, the cam pins 3-97 operates to return the split mold 358 into its closed position for purposes of molding the neck.

In the embodiment of FIGS. 16 and 17, at least two and in some instances several rows of core rod assemblies 426 may be provided at each station. Otherwise, reference should be made to the embodiment of FIGS. 1 to 8 for details; and as in the case of the previous embodiment, similar numbers will be employed increased by 400. Suffice it to say that the manifold at the injection station 320 may parallel that discussed in the aforenoted patent. At the blowing station 322, each mold halve may be independently actuated by its own hydraulic cylinder, or corresponding halves may be coupled or linked as shown to a common cylinder.

Thus, the several aforenoted objects and advantages are most effectively attained. In addition, the following contributions afforded by the present invention should be noted:

(1) It is possible to produce jars, bottles, cups, tubs, I

either with small necks, large bodies, or large openings and tapered bodies, as Well as the same products capable of being made on commercially available injection blow molding machinery, extrusion blow machines, thermoforming machines, and injection molding machines.

(2) It is possible to produce containers with wall thicknesses ranging between .003 to more than .250 inch.

(3) It is possible to incorporate more mold cavities in a relatively small area than available injection blow molding systems. Therefore, the apparatus of the present invention is more productive. Towards this end, several rows of molds may be incorporated and therefore even higher production rates are possible.

(4) It is possible to employ faster cycle times particularly in view of the one piece solid traveling neck mold which provides the best heat transfer system. This is also true for the one piece solid injection mold and core rod assemblies.

(5) Molding and clamping forces are better controlled compared to prior art systems particularly in view of the fact that during the injection cycle the injection forces and the clamping forces are in the same direction at the injection station.

(6) The apparatus and process of injection molding is not only simpler than that of existing equipment but facilitates the attainment of better control over shot size, pressure, parison temperature and uniformity. In addition, less expensive yet longer lasting molds may be employed.

(7) The solid one piece neck mold reduces cost because it is not split and the one mold is associated with the container neck throughout the entire molding process. This neck also provides uniform common cooling around the entire periphery of the neck. No parting lines and consequently flashes are possible. Cycle time is also reduced because of the utilization of this type of neck mold. Therefore, special neck clamp mechanisms are eliminated as well as the need for more than one neck mold to be associated with the neck of the container during the molding process. The neck mold also permits accurate control over neck dimensions and the maintenance of the prescribed tolerances.

(8) Automation is enhanced as a result of the novel unscrewing mechanisms herein. Furthermore, safety is provided by positive ejection of unblown parison and/or blown parts.

(9) Through orientation and stretching, the blow-up factor may be increased many fold and certainly by at least a factor of two. Wall thickness of the finished product is also more closely controlled.

Although several somewhat preferred embodiments have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.

I claim:

1. A method of injection blow molding comprising:

injection molding a parison about a core at an injection molding station into a selected configuration without a parting line, said injection molding including clamping an injection mold having a one piece female mold and one piece core closed at the injection station so that clamping forces are in a direction parallel to the axis of the core and injecting plastic into the injection mold to form the parison, the forces of clamping and injection being in substantially the same direction and the injecting forces being in a direction counter to that of the clamping forces;

blow molding the parison while on the core at a spaced blowing station into the selected finished product; removing the finished product at a spaced ejection station;

indexing the parison about a rotational axis parallel to the axis of said core from the molding station to the blowing station and the finished product from the blowing station to the ejection station and following said indexing the steps of injection molding, blow molding, and removing the finished production being carried on substantially simultaneously in regard to the production of other of said products; and

moving the core axially towards and away from said stations following each of the defined indexing steps.

2. The invention in accordance with claim 1 including the steps of:

the finished product being a container with a neck with means for coupling to a closure, and molding the neck when forming the parison with a neck mold, and maintaining the neck mold about the formed threaded neck while indexing the parison to the blow station and the finished product to the ejection station prior to removal of the finished product.

3. The invention in accordance with claim 2 wherei the parison and neck thereon are formed without a mold parting line at the injection station.

4. The invention in accordance with claim 3 wherein the container neck is threaded and is unscrewed from the neck mold for removal at the ejection station.

5. The invention in accordance with claim 1 wherein the parison is oriented between injection molding and blowing to improve its mechanical and temperautre characteristics for blowing.

6. The invention in accordance with claim 5 wherein the parison is initially expanded slightly by air-pressure and thereafter by mechanical stretching prior to blowing.

7. The invention in accordance with claim 6 wherein the parison blow-up ratio is increased by at least a factor of two. 1

8. The invention in accordance with claim 1 wherein rows of parisons are injection molded at the injection molding station.

References Cited UNITED STATES PATENTS 2,853,736 9/1958 Gussoni 264-97 UX 3,609,803 10/1971 Fattori 26497 X 3,100,913 8/1963 De Matteo 425324 X 2,331,687 10/1943 Hobson 26497 3,412,188 11/1968 Seefiuth 26497 X 3,470,282 9/ 1969 Scalora 264-97 ROBERT F. WHITE, Primary Examiner I. H. SILBAUGH, Assistant Examiner U.S. Cl. X.R.

26497; 425324 B, Dig. 205, Dig. 209, Dig. 211, Dig. 215, Dig. 216

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